Several patents, patent applications and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents, patent applications and publications is incorporated by reference herein.
Ionomers are copolymers produced by partially or fully neutralizing the carboxylic acid groups of precursor or parent polymers that are acid copolymers comprising copolymerized residues of α-olefins and α,β-ethylenically unsaturated carboxylic acids. A variety of articles made from ionomers by injection molding processes have been used in our daily life.
For example, golf balls with ionomer-containing covers have been produced by injection molding. See, e.g.; U.S. Pat. Nos. 4,714,253; 5,439,227; 5,452,898; 5,553,852; 5,752,889; 5,782,703; 5,782,707; 5,803,833; 5,807,192; 6,179,732; 6,699,027; 7,005,098; 7,128,864; 7,201,672; and U.S. Patent Appln. Pubin. Nos. 2006/0043632; 2006/0273485; and 2007/0282069.
Ionomers have also been used to produce injection molded hollow articles, such as containers. See, e.g., U.S. Pat. Nos. 4,857,258; 4,937,035; 4,944,906; 5,094,921; 5,788,890; 6,207,761; and U.S. Pat. No. 6,866,158, U.S. Patent Publication Nos. 20020180083; 20020175136; and 20050129888, European Patent Nos. EP1816147 and EP0855155, and PCT Patent Publn. Nos. WO2004062881; WO2008010597; and WO2003045186.
In addition, the use of ionomers for packaging films, injection molded articles, and other end-uses is well known in the art. Some films are designed to be breathable, to allow oxygen and/or moisture to pass through, to exhibit elastic properties, or to protect the materials they surround. See, for example, U.S. Pat. Nos. 7,438,940 and 7,635,509; and U.S. Patent Appln. Publn. Nos. 2006/0094824 and US2010/0272898. Ionomeric materials can also be used to fabricate blown films and thermoformed articles. See, for example, U.S. Patent Appln. Publn. Nos. 2011/0028622 and 2009/0099313 and U.S. Pat. No. 8,110,138.
There remains a need, however, for polymers having improved optical properties. For example, containers produced by injection molding often have thick wall structures. When ionomers are used in forming such injection molded containers, the optical properties may suffer due to the thickness of the wall. There is a need, especially in the cosmetics industry, to develop containers and films that are made of ionomer compositions and that have improved optical properties.